Moore's Law has allowed processors in mobile devices to be used for ever more complex processing, such as the processing of full motion video for display on mobile devices. However, while Moore's Law enables the processor to exponentially increase in processing power, the same is not true in the transmission of data. The transmission of full motion video requires thousands of times more data than the transmission of text, or even voice. Each transmitted bit still takes approximately the same amount of power to transmit and receive. In addition, the available bandwidth for data communication has remained relatively fixed. In order to accommodate the large increase in data transmission, the efficient use of the available radio network resources is important. To handle the increasing amount of wireless services and data transmission for an increasing numbers of users, efficient use of the available radio network resources has become important.
In homogeneous networks, the transmission station, also referred to as a macro node, can provide basic wireless coverage to mobile devices over a broad geographical area by transmitting a relatively high power signal. However, the geographical area can still have areas in which wireless communication is slow or difficult, due to high use, changes in geography, large buildings, and so forth. Heterogeneous networks (HetNets) were introduced to compensate for areas in which communication was slow or nonexistent and to reduce increased traffic loads on the macro node due to increased usage and functionality of mobile devices. HetNets can include a layer of planned high power macro nodes or macro evolved node Bs (eNode Bs) overlaid with layers of lower power nodes (micro-nodes, pico-nodes, femto-nodes, home-nodes, relay stations, etc. . . . ) that can be deployed in a less well planned or even entirely uncoordinated manner within the coverage area of the macro nodes. The macro nodes can be used for basic coverage, and the low power nodes can be used to fill coverage holes, to improve capacity in hot-zones or at the boundaries between the macro nodes' coverage areas, and improve indoor coverage where building structures impede signal transmission.
However, even with a targeted deployment of lower power nodes, most users will still receive a stronger signal or have a greater downlink capacity from the relatively high power signal of the macro-node. For a more balanced use of nodes in a HetNet, such as to balance the traffic load for a given node, user equipment (UE) association with selected nodes can reduce the load on nodes such as macro nodes, allowing for users to be better served.
Several approaches to node association and radio access technology (RAT) selection have emerged for different embodiments of multiple radio access technology (multi-RAT) HetNet architectures to better distribute traffic across the overall network. A multi-RAT HetNet architecture is a HetNet that includes multiple nodes that support different types of radio access technologies. The RATs may operate in licensed and/or unlicensed bands. A multi-RAT HetNet can support licensed band technologies, such as 3rd Generation Partnership Project (3GPP) technologies, and unlicensed band technologies, such as Institute of Electronics and Electrical Engineers (IEEE) 802.11 WiFi technologies. Additional types of licensed and unlicensed bands can also be supported, as discussed in the proceeding paragraphs.
Node-range extensions schemes have been designed to work with single-RAT HetNets, wherein signal to noise ratio (SNR) based node association schemes are extended to steer traffic away from macro nodes to small nodes. Node associations which have been designed for HetNets incorporating multiple RATs were typically developed to account for Quality of Service (QoS) in node-association. Other load balancing techniques have been designed for multi-RAT HetNets. Network controlled node-selection and assignment mechanisms for integrated multi-RAT HetNets, which optimize loading across multiple RATs of an integrated small nodes have been developed. Centralized solutions for node-association and RAT selection for macro assisted HetNets have also been designed. Fully distributed UE centric schemes have been designed wherein RAT selection is performed without any help from the network.
Additionally, network cooperation is very limited in availability and feasibility for these designs. For example, planned operator deployments for multi-RAT HetNets include distributed deployments wherein the access points (APs) or eNode Bs are not necessarily co-located and no direct network interface exists between them, e.g. no network interface exists between the third generation partnership project (3GPP) nodes and the wireless local area network (WLAN) APs. Furthermore UE assistance creates overhead associated for these schemes.
Each node selection scheme has a distinct approach to signal network assistance information and employ different methods by which such information is used by UEs in their network selection decisions. Additionally, the performances of these designs deviate substantially from the optimal solution available with full network cooperation. Furthermore, with all the variations in the designs it has become cumbersome for a UE to incorporate and/or use the information from the different designs.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.